Blind stitch sewing mechanism for a sewing machine

ABSTRACT

A blind stitch sewing mechanism for a sewing machine includes a curved, oscillating needle, and a looper, having only one degree of freedom, for cooperatively forming a blind stitch with the curved oscillating needle.

FIELD OF THE INVENTION

[0001] The present invention generally relates to sewing machines and, more particularly, to a blind stitch sewing mechanism for a sewing machine.

BACKGROUND OF THE INVENTION

[0002] In the mattress industry, there is a manufacturing operation that requires a unique sewing process to achieve what could only be formerly produced with hazardous and volatile adhesives. The operation requires the attachment of a first piece of material to the underside of a second piece of material, without any indication of the attachment from the finished side. A conventional sewing machine would pierce both sides of the second piece of material, forming a stitch visible from either side of the second piece of material.

[0003] The most apparent solution was to use what is referred to as a “blind stitch” sewing machine, which was previously developed for the garment and light textile industries. The blind stitch sewing machine was primarily used to sew the hems of pants, skirts, curtains, and other light goods such that the stitch could not be seen on the outside. The needle depth was regulated with a fine depth control, allowing operators to just pierce the first few threads of the outer layer, preserving the finished look of the material on the outside.

[0004] Manufacturers in the mattress industry soon saw the advantages of this type of approach, and created a demand for a “mattress panel” grade sewing workstation to assist their operations. Most iterations of this workstation closely resembled the original apparel unit, with various feed-assist devices attached to help pull the material through a machine that was incapable of manipulating the ten or more pound panels being forced through them.

[0005] An awareness of the original blind stitch sewing machine's complexity also began to develop, as units were run to the brink of their mechanical abilities. The original blind stitch sewing machine (described further herein below) required an inherently complex and often times counter-intuitive mechanism to develop the motion necessary to form the blind stitch. Adjustments made to these machines sometimes affected the machines in such a way that entire machines needed to be sent back to the original manufacturer for re-timing and set up.

[0006]FIG. 1 is a diagram illustrating a portion of a blind stitch sewing machine, according to the prior art. In the conventional blind stitch sewing machine, there is a curved needle 105 that travels in an arc 101, stopping at two points (A, B). There is a forked “looper” 110 that meets up with the needle 105 at its two different stop locations. The forked looper 110, while moving on the arc 101, also “flip flops” on an axis best described as “in and out” of the page. Thus, if the horizontal axis is considered the “x-axis” and the vertical axis is considered the “y-axis”, then the forked looper 110 can be considered to move along the “z-axis” while also moving along the arc 101 (which is parallel to the horizontal or x-axis). Accordingly, the forked looper 110 can be considered to have two degrees of freedom, one along the x-axis and the other along the z-axis. While the forked looper 110 is at point A, the looper 110 is “bottom up”. At point B, the forked looper 110 is “bottom down”. Thus, while the forked looper 110 is moving along the arc 101, the forked looper 110 also moves in and out of the page as well (i.e., along the z-axis). When the needle 105 is sitting at point B, the forked looper 110 actually slides forward out of the page and “shovels” the thread 170 off of a flat spot on the needle 105, grabbing the thread 170 and carrying the thread 170 back over the material as the needle 105 travels along its arc 101 to point A. At point A, the needle 105 then travels between the two tines of the forked portion of the forked looper 110, and forms a “knot” through the loop of the thread 170 that was picked up during the “shovel” process at point B previously.

[0007] The material is forced up through a groove in a throat plate 115 by a smooth polished rib 120 from below, that is spring pressured upwards. The objective is to connect a first piece 191 of material (e.g., border material) to a second piece 191 of material (e.g., quilted panel material) without showing the stitch from the other side; in this case, the bottom (i.e., finished) side 199. The polished rib 120 is designed so as to not leave a mark or dent in the finished side 199 of the material.

[0008] There are numerous eccentric drivers (not shown) required to develop the astoundingly complex, timed motion of the forked looper 110, any one of which if misadjusted could have an extremely adverse affect on the timing of the sewing machine.

[0009] Accordingly, it would be desirable and highly advantageous to have a blind stitch sewing mechanism for a sewing machine that overcomes the above-described problems of the prior art.

SUMMARY OF THE INVENTION

[0010] The problems stated above, as well as other related problems of the prior art, are solved by the present invention, a blind stitch sewing mechanism for a sewing machine.

[0011] According to an aspect of the present invention, there is provided a blind stitch sewing mechanism for a sewing machine. The blind stitch sewing mechanism includes a curved, oscillating needle, and a looper, having only one degree of freedom, for cooperatively forming a blind stitch with the curved oscillating needle.

[0012] According to another aspect of the present invention, there is provided a blind stitch sewing mechanism for a sewing machine. The blind stitch sewing mechanism includes a curved needle for oscillating back and forth between an ascended position and a descended position. The blind stitch sewing machine further includes a butterfly looper having a main body portion, a hook, and a central axis of rotation. The butterfly looper lifts a thread off of the curved needle using the hook and wraps the thread around the main body portion by rotating along the central axis, when the curved needle is oscillating to the descended position. A knot is formed when the curved needle is oscillating to the ascended position.

[0013] These and other aspects, features and advantages of the present invention will become apparent from the following detailed description of preferred embodiments, which is to be read in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0014]FIG. 1 is a diagram illustrating a portion of a blind stitch sewing machine, according to the prior art;

[0015]FIG. 2 is a diagram illustrating a portion of a blind stitch sewing mechanism for a sewing machine, according to an illustrative embodiment of the present invention;

[0016] FIGS. 3-6 illustrate a cycle of a needle relative to a butterfly looper, according to an illustrative embodiment of the present invention; and

[0017] FIGS. 7-11 are diagrams illustrating a cycle of a needle relative to a looper other than a butterfly looper to which the present invention may be applied, according to an illustrative embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0018] The present invention is directed to a blind stitch sewing mechanism for a sewing machine. The present invention is capable of handling the heaviest workloads and speeds required in sewing, e.g., border material to a quilted panel of a mattress without puncturing the quilted panel or leaving a visible mark on the finished side of the quilted panel. Moreover, the present invention is significantly less complex than prior art blind stitch sewing mechanisms.

[0019] A blind stitch operation is a “chain stitch” operation that uses only one thread to form the stitch. A blind stitch is the type of stitch that can be completely unraveled and pulled out, like a thread in a sweater in a cartoon. A similar “one thread” operation was used in the sewing of buttons to garments, and utilized a unique looper called a “butterfly” looper, named in part due to its unique shape. The butterfly looper was adapted for use in the present invention, and is described in that regard with respect to FIGS. 2-6. It is to be appreciated that while the present invention is primarily described herein with respect to the butterfly looper, any type of looper having only one degree of freedom may also be readily employed in accordance with the present invention, while maintaining the spirit and scope of the present invention. By employing a looper having only one degree of freedom, many significant advantages are gained over the forked looper of the prior art that has two degrees of freedom. For example, the use of a looper having only one degree of freedom results in a tremendous reduction in complexity over the forked looper of the prior art. For a looper other than a butterfly looper that also has only one degree of freedom, such one degree of freedom may correspond, e.g., to movement of the looper along an arc for the purpose of sewing a blind stitch. This differs from the butterfly looper described below in that the butterfly looper moves rotably along an axis that passes through the butterfly looper. FIGS. 7-11 are diagrams illustrating a cycle of a needle relative to a looper other than a butterfly looper to which the present invention may be applied, according to an illustrative embodiment of the present invention. It is to be appreciated that the looper 700 shown in FIGS. 7-11 has only has one degree of freedom similar to a butterfly looper. The looper 700 manipulates thread 170 with respect to a needle 105 to form a blind stitch.

[0020]FIG. 2 is a diagram illustrating a blind stitch sewing mechanism 200 for a sewing machine, according to an illustrative embodiment of the present invention. The blind stitch sewing mechanism 200 includes a butterfly looper 210. The butterfly looper 210 in FIG. 2 replaces the forked looper 110 used in the prior art blind stitch sewing machine shown in FIG. 1. It is to be appreciated that the use of the butterfly looper 210 provides a significantly less complex but more robust approach to sewing blind stitches than the prior art. For example, the butterfly looper 210 has only one degree of freedom, namely, rotation along its central axis. In contrast, the forked looper 110 of FIG. 1 has two degrees of freedom, namely “flip-flopping” along the z-axis and arcing along the y-axis.

[0021] FIGS. 3-6 illustrate a cycle of the needle 105 relative to the butterfly looper 210, according to an illustrative embodiment of the present invention. FIG. 3 illustrates the needle 105 beginning its descent down into the material penetration area. The butterfly looper 210 is turning its point to prepare to meet the needle 105.

[0022]FIG. 4 illustrates the needle 105 “bottomed out” in the penetration area, and rising up through the guide hole into the butterfly looper area. The butterfly looper 210 has almost turned to meet up its pointed hook with the needle 105.

[0023]FIG. 5 illustrates the needle 105 fully penetrated and at the top of its stroke. Notice the center hole in the butterfly looper 210. The center hole allows the needle 105 to reach its peak without hitting the butterfly looper 210. This clearance is unique to the butterfly looper 210.

[0024]FIG. 6 illustrates the hook of the butterfly looper 210 just skimming the flat of the curved needle 105, lifting the thread off of the back of the needle 105 and beginning to wrap it around the body of the butterfly looper 210. When the needle 105 returns again, this wrap will fall off of the butterfly looper 210 and form the knot, similar to the forked looper 110 of the prior art.

[0025] Notice the simplicity of the timing. A mechanic needs only loosen a set screw 265 in a butterfly looper holder 260, and adjust the point of the hook angularly so as to catch the thread off of the back of the butterfly looper 210. It is to be appreciated that while the adjustments to the butterfly looper 210 are described herein with respect to a set screw 265, other arrangements and/or physical structures may be employed to provide angular adjustment to the butterfly looper 210 as readily contemplated by one of ordinary skill in the related art.

[0026] Although the illustrative embodiments have been described herein with reference to the accompanying drawings, it is to be understood that the present invention is not limited to those precise embodiments, and that various other changes and modifications may be affected therein by one of ordinary skill in the related art without departing from the scope or spirit of the invention. All such changes and modifications are intended to be included within the scope of the invention as defined by the appended claims. 

What is claimed is:
 1. A blind stitch sewing mechanism for a sewing machine, comprising: a curved, oscillating needle; and a looper, having only one degree of freedom, for cooperatively forming a blind stitch with said curved oscillating needle.
 2. The blind stitch sewing mechanism according to claim 1, wherein said looper has an aperture for allowing said curved, oscillating needle to pass there through.
 3. The blind stitch sewing mechanism according to claim 1, wherein said looper has a hook for lifting a thread off of said curved, oscillating needle and wrapping the thread around said looper.
 4. The blind stitch sewing mechanism according to claim 3, wherein the hook wraps the thread around said looper to form a knot.
 5. The blind stitch sewing mechanism according to claim 3, further comprising a looper holder and a set screw for collectively maintaining a position of the looper holder, and wherein said set screw further allows for angular adjustment of the hook.
 6. The blind stitch sewing mechanism of claim 1, wherein said looper has a central axis, and the only one degree of freedom corresponds to rotation of the looper around the central axis.
 7. The blind stitch sewing mechanism of claim 1, wherein said looper is a butterfly looper.
 8. The blind stitch sewing mechanism of claim 1, wherein the only one degree of freedom corresponds to movement of the looper along an arc.
 9. A blind stitch sewing mechanism for a sewing machine, comprising: a curved needle for oscillating back and forth between an ascended position and a descended position; and a butterfly looper having a main body portion, a hook, and a central axis of rotation, said butterfly looper for lifting a thread off of said curved needle using the hook and wrapping the thread around the main body portion by rotating along the central axis, when the curved needle is oscillating to the descended position, and wherein a knot is formed when the curved needle is oscillating to the ascended position.
 10. The blind stitch sewing mechanism of claim 9, wherein said butterfly looper has an aperture for allowing said curved needle to pass there through when said curved needle is oscillating.
 11. The blind stitch sewing mechanism of claim 9, further comprising a butterfly looper holder and a set screw for collectively maintaining a position of the butterfly loop holder, and wherein said set screw further allows for angular adjustment of the hook.
 12. A method for sewing a blind stitch on a sewing machine, comprising the steps of: providing a curved needle; providing a butterfly looper having a central axis, a hook, and a main body portion; oscillating the curved needle back and forth between an ascended position and a descended position; rotating the butterfly looper along the central axis so as to lift a thread off of the curved needle using the hook and wrap the thread around the main body portion, when the curved needle is oscillating to the descended position, and wherein a knot is formed when the curved needle is oscillating to the ascended position.
 13. The method of claim 12, wherein the butterfly looper has an aperture, and said oscillating step comprises the step of passing the curved needle through the aperture.
 14. The method of claim 12, further comprising the step of providing a capability to adjust an angular position of the butterfly looper.
 15. The method of claim 12, further comprising the step of providing a capability to adjust an angular position of the butterfly looper via a single set screw.
 16. A method for sewing a blind stitch on a sewing machine, comprising the steps of: providing a curved needle; providing a looper having only one degree of freedom; oscillating the curved needle back and forth to form a blind stitch by lifting a thread off of the needle and forming a knot.
 17. The method of claim 16, further comprising the step of providing a capability to adjust an angular position of the looper.
 18. The method of claim 16, further comprising the step of providing a capability to adjust an angular position of the butterfly looper via a single set screw. 